1. Field of the Invention
The present invention generally relates to a control technology, and more particularly, to a control technology of light emitting diode channels (LED channels).
2. Description of Related Art
Along with the upgrowth of the semiconductor industry and the related electronic industry, many digital means, such as mobile phone, digital camera, digital video camera, notebook and desktop computer, have been getting continuous evolutions and improvements towards more usage convenience, multi functions and stylish design. In order to use the information products, a displaying screen is an indispensable man-machine interface, by which a user can more conveniently manipulate the above-mentioned apparatuses. Among various displaying screens, the liquid crystal display (LED) has played a major role in the market. However, an LED is not self-luminescent, so that a backlight module must be employed and placed under the LED, which serves as a light source so as to make display possible.
FIG. 1 is a diagram of a conventional backlight module and a controlling circuit thereof. Referring to FIG. 1, a conventional backlight module usually comprises a plurality of LED channels 21-2x, wherein the LED channels 21-2x are respectively connected in series to a plurality of current sources 31-3X and the connected current sources 31-3X can respectively control the currents flowing the LED channels 21-2x. The circuit for detecting short-circuit/open-circuit 10 in FIG. 1 can detect a plurality of voltages Ch1-Chx so as to judge whether or not the LED channels 21-2x are short or open.
FIG. 2 is a diagram of the circuit for detecting short-circuit/open-circuit in FIG. 1. Referring to FIGS. 1 and 2, a comparator 41 compares the voltage Ch1 with a voltage Vref_short. When the voltage Ch1 is higher than the voltage Vref_short, the comparator 41 outputs a signal short to indicate the LED channel 21 is short already. Analogically for the comparators 42-4x, the signal short output from an OR gate 61 is for indicating one of the LED channels 21-2x has short-circuit.
On the other hand, a comparator 51 compares the voltage Ch1 with a voltage Vref_open. When the voltage Ch1 is lower than the voltage Vref_open, the comparator 51 outputs a signal short to indicate the LED channel 21 is open already. Analogically for the comparators 52-5x, the signal open output from an OR gate 62 is for indicating one of the LED channels 21-2x has open-circuit.
It should be noted that in the prior art, the quantity of the comparators is increased with the increasing quantity of the LED channels. However, since the comparators 42-4x and the comparators 52-5x are analog circuits, so that the circuit area thereof is considerably large with the increasing quantity thereof. In addition, the hardware cost would accordingly soars, which is disadvantageous for the circuit layout.